DISEASE CHARACTERISTICS: Diagnosis of locally advanced or metastatic breast cancer High likelihood of anthracycline resistance due to prior anthracycline exposure in the adjuvant or metastatic setting Prior anthraquinone (e.g., mitoxantrone) insufficient Prior cumulative anthracycline dose limited to doxorubicin-equivalent 350 mg/m2 by IV bolus or 450 mg/m2 by prolonged (at least 48 hours) infusion Measurable or evaluable disease Brain metastases treated by prior surgery and/or radiotherapy allowed if neurologic status stable 2 weeks after discontinuation of dexamethasone Hormone receptor status: Not specified